TRPV4 channel activation selectively inhibits tumor endothelial cell proliferation.

Roslin J Thoppil,Holly C Cappelli,Vinay Kondeti,Sailaja Paruchuri,Andrew C Dudley,Ravi K Adapala,J Gary Meszaros,Charles K Thodeti

doi:10.1038/srep14257

Abstract

Endothelial cell proliferation is a critical event during angiogenesis, regulated by both soluble factors and mechanical forces. Although the proliferation of tumor cells is studied extensively, little is known about the proliferation of tumor endothelial cells (TEC) and its contribution to tumor angiogenesis. We have recently shown that reduced expression of the mechanosensitive ion channel TRPV4 in TEC causes aberrant mechanosensitivity that result in abnormal angiogenesis. Here, we show that TEC display increased proliferation compared to normal endothelial cells (NEC). Further, we found that TEC exhibit high basal ERK1/2 phosphorylation and increased expression of proliferative genes important in the G1/S phase of the cell cycle. Importantly, pharmacological activation of TRPV4, with a small molecular activator GSK1016790A (GSK), significantly inhibited TEC proliferation, but had no effect on the proliferation of NEC or the tumor cells (epithelial) themselves. This reduction in TEC proliferation by TRPV4 activation was correlated with a decrease in high basal ERK1/2 phosphorylation. Finally, using a syngeneic tumor model revealed that TRPV4 activation, with GSK, significantly reduced endothelial cell proliferation in vivo. Our findings suggest that TRPV4 channels regulate tumor angiogenesis by selectively inhibiting tumor endothelial cell proliferation.

Highlights

Express reduced levels of TRPV4 compared to normal endothelial cells (NEC), and exhibit abnormal Rho-dependent mechanosensing and angiogenesis, which were restored upon overexpression or pharmacological activation of TRPV415
We investigated if tumor endothelial cells (TEC) proliferation levels are altered compared to NEC, which may contribute to the abnormal angiogenesis and structure of tumor vessels
Western blot analysis revealed that expression of proliferating cell nuclear antigen (PCNA) is increased in TEC compared to NEC (p ≤ 0 .05; Fig. 1C)

Summary

Introduction

Express reduced levels of TRPV4 compared to normal endothelial cells (NEC), and exhibit abnormal Rho-dependent mechanosensing and angiogenesis, which were restored upon overexpression or pharmacological activation of TRPV415. Results TEC exhibit increased proliferation which is reduced by pharmacological activation of TRPV4. We found that TEC exhibited significantly (p ≤ 0.05) increased proliferation compared to NEC, as measured by XTT and cell viability assays (Fig. 1A,B).

Results

Conclusion